General mechanisms of drought response and their application in drought resistance improvement in plants

Plants often encounter unfavorable environmental conditions because of their sessile lifestyle. These adverse factors greatly affect the geographic distribution of plants, as well as their growth and productivity. Drought stress is one of the premier limitations to global agricultural production due to the complexity of the water-limiting environment and changing climate. Plants have evolved a series of mechanisms at the morphological, physiological, biochemical, cellular, and molecular levels to overcome water deficit or drought stress conditions. The drought resistance of plants can be divided into four basic types-drought avoidance, drought tolerance, drought escape, and drought recovery. Various drought-related traits, including root traits, leaf traits, osmotic adjustment capabilities, water potential, ABA content, and stability of the cell membrane, have been used as indicators to evaluate the drought resistance of plants. In the last decade, scientists have investigated the genetic and molecular mechanisms of drought resistance to enhance the drought resistance of various crops, and significant progress has been made with regard to drought avoidance and drought tolerance. With increasing knowledge to comprehensively decipher the complicated mechanisms of drought resistance in model plants, it still remains an enormous challenge to develop water-saving and drought-resistant crops to cope with the water shortage and increasing demand for food production in the future.     

Naturally occurring heterocycles inducing drought resistance in plants

Summary During screening of animal metabolites which induce drought resistance in plants, two diketopiperazines, cyclo(L-Hyp-L-Pro) (1) and cyclo(L-Hyp-L-Leu) (2), emerged as effective. When rice seeds were pretreated with the cyclic dipeptides (1 and2) during their germination period, the resulting seedlings showed significant resistance to water-stress caused by 0.5–1.5% NaCl solution or 2.5–5.0% mannitol solution.     

Enzymatic synthesis and destruction of carotenoids in mango extracts

Zusammenfassung Eine Biosynthese von Carotin lässt sich in zellfreien karotenoidhaltigen Extrakten reifer Mangofrüchte bei Gegenwart von Glucose oder Azetat beobachten. Dabei zeigt sich gleichzeitig eine Abnahme der Karotenoide.     

Electrolytic behaviour of some carotenoids in strongly acid media

Zusammenfassung Carotinoide und Carotinoid-Epoxyde bilden mit verschiedenen Säuren und Salzen intensiv blau gefärbte Produkte, deren Natur unbekannt ist. Das elektrolytische Verhalten dieser Stoffe wird untersucht, und es wird festgestellt, dass die Wanderungsrichtung in hohem Mass davon abhängt, ob die Behandlung der Carotinoide mit Säuren in wässeriger oder in wasserfreier alkoholischer Lösung vorgenommen wurde.     

Disposition of carotenoids in the blue goose barnacleLepas fascicularis

Zusammenfassung Die blauen ozeanischen Cirripedien,Lepas fascicularis, speichern Karotinoide in Eiern, Eingeweiden und den meisten übrigen Geweben in den folgenden ungefähren Konzentrationen: 5:2:1 mg/100 g. In jeder Art von Gewebe ist Astaxanthin das Hauptkarotinoid, welches meist in Form des blauen Chromproteins vorliegt. Kleinere Mengen von Karotin und etwas mehr Xanthophylle kommen in den Eingeweiden, nicht aber in den reifen Eiern vor.

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Contribution from the Scripps Institution of Oceanography. This research was supported by Research Grant No. GB-5332X from the National Science Foundation. We are indebted also toJoanne Rhoads andP. Wiebe for donating some of the fresh barnacle specimens, and to Dr.W. A. Newman for his help and information concerning the biology and dissection of this barnacle.     

LSD induced chlorophyll mutations in barley

Summary In earlier reports, LSD was found to induce extensive chromosomal aberrations in barley. With the same dose it is now observed that LSD is potent in the induction of chlorophyll mutations. This may be the first evidence that the drug induces gene mutations in plants.Acknowledgent. We are grateful to Dr H.K. Jain, Indian Agricultural Research Institute, for his interest and guidance.     

Rapid preparation of pure chlorophyll a

Summary Very pure chlorophyll a has been obtained from blue-green algae by a simple precipitation procedure. Its purity is at least equal to that of chlorophyll a obtained from spinach by conventional chromatography.Acknowledgments. This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung of the Republic of Austria. We thank Dr H. Springer-Lederer for helpful comments and Prof. E. Broda for his interest.     

Mechanism of potassium deficiency-induced retardation of chlorophyll biosynthesis in Zea mays

Summary Potassium deficiency decreased the formation of protochlorophyll and retarded the rate of transformation of protochlorophyll to chlorophyll in maize seedlings.     

The interaction of a gibberellin and a kinin in the control of chlorophyll synthesis

Resumé La promtion synergétique et l'inhibition de la synthèse de la chlorophylle par la gibberelline (GA₃) et par la 6-benzylaminopurine (6-BAP) de concentrations diverses, fut observée. L'augmentation de la concentration de 6-BAP réduisit la concentration de GA₃ nécessaire pour obtenir la promotion maximum.     

On the location of the tetrapyrrole macrocycle of chlorophyll a in phospholipid vesicles and in hexadecane

Summary The state of chlorophyll a in phosphatidylcholine vesicles was examined. The results indicate that the chlorophylls are present in monomeric form. A kinetic study of chlorophyll reactions with K₂S₂O₈ and piperidine showed that these substances react with the porphyrin rings of pigments located on both vesicle faces, most probably within the polar headgroup region.Acknowledgments. This work was supported by the Research Committee and the Biophysics Research Group, University of Québec at Trois-Rivières.     

Structural characteristics of the carotenoids binding to the blue carotenoprotein fromProcambarus clarkii

Summary A blue carotenoprotein from the crayfishProcambarus clarkii was extracted and purified. This carotenoprotein contains the carotenoid astaxanthin as a prosthetic group. In the present work we have identified by reconstitution, after removing the native carotenoid, some characteristics of the carotenoids that could bind to the apoprotein. The carotenoid must have two oxo groups at positions 4, 4 and two hydroxyl groups at positions 3, 3 the hexagonal or pentagonal end structure being indifferent. It has been proved that changes in the polyene chain structure such as triple bonds destroy this binding capacity.     

Induction of chromosome aberrations and chlorophyll mutations in plants by methylisocyanate (MIC) gas

Summary Seeds ofSolanum surattense Burm. f. collected from areas of Bhopal (India) affected by methylisocyanate gas showed chromosome aberrations in root cells, and growth retardation and chlorophyll mutation of seedlings, the frequencies of which varied from one locality to another.     

The presence of carotenoids in eggs deposits of theChironomus annularius meig (Diptera: Chironomidae)

Résumé A l'aide de la Chromatographie sur colonne et sur couche fine, les auteurs ont effectué la séparation des caroténoïdes des ufs deChironomus annularius Meig (Diptera: Chironomidae). Ces recherches ont attesté la présence du -carotene, de l'échinénone, de la cryptoxanthine et de la lutéine.     

Dietary carotenoids block photocarcinogenic enhancement by benzo (a)pyrene and inhibit its carcinogenesis in the dark

The carotenoids beta-carotene (C) and canthaxanthine (CX), with and without pro-vitamin A activity, respectively, when perorally administered to mice, markedly prevent benzo(a)pyrene photocarcinogenic enhancement (BP-PCE), continue to block such BP-PCE and protect significantly against BP carcinogenesis in mice maintained in the dark. These results appear relevant to both the pathogenesis of chemical carcinogenesis and rational programs of skin cancer prevention in humans.     

Telomerase and drug resistance in cancer

It is well known that a decreased expression or inhibited activity of telomerase in cancer cells is accompanied by an increased sensitivity to some drugs (e.g., doxorubicin, cisplatin, or 5-fluorouracil). However, the mechanism of the resistance resulting from telomerase alteration remains elusive. There are theories claiming that it might be associated with telomere shortening, genome instability, hTERT translocation, mitochondria functioning modulation, or even alterations in ABC family gene expression. However, association of those mechanisms, i.e., drug resistance and telomerase alterations, is not fully understood yet. We review the current theories on the aspect of the role of telomerase in cancer cells resistance to therapy. We believe that revealing/unravelling this correlation might significantly contribute to an increased efficiency of cancer cells elimination, especially the most difficult ones, i.e., drug resistant.     

基于高光谱的柑橘树红边特征及叶绿素和LAI的监测

为从光谱信息中寻找最能反映叶面积指数（LAI）的参数并建立模型,文中以砂糖橘树与年橘树为实验对象,通过室外实验,同步测定柑橘树冠层在不同生育期的高光谱反射率、红边参数和叶片的叶绿素含量及LAI.结果表明,柑橘树冠层光谱红边具有"双峰"和"红边平台"现象,红边位置λ_red位于695～724 nm之间.红边幅值Dλ_red和红边面积S_red有"红移"和"蓝移"现象;叶面积指数与冠层光谱红边参数λ_red,Dλ_red,S_red之间显著相关.利用柑橘树冠层的五种光谱形式,分别与叶面积指数进行逐步回归相关分析并与LAI建立模型;叶片叶绿素含量与其反射光谱的λ_red,Dλ_red,S_red也显著相关.     

Protection of chlorophyll a from photo-oxidation byβ-carotene in binary mixture of organic solvents

Zusammenfassung Das photoxytadive Ausbleichen des Chlorophylls a wird durch die Gegenwart des-Carotins gehemmt. Die Hemmwirkung des-Carotins und die Wechselwirkung zwischen Chlorophyll a und-Carotin werden vom Lösungsmittel kontrolliert.     

黄瓜叶片叶绿素荧光光谱日变化的研究

文中研究了叶绿素荧光光谱的日变化规律,分析了叶片的光合速率与叶绿素荧光光谱之间的关系,通过分析日光温室光合有效辐射的变化规律,建立叶片光合速率与叶绿素荧光光谱强度之间的回归方程.利用激光诱导叶绿素荧光光谱分析技术实现对叶片光合速率的无损检测,为产量预测的研究奠定了基础,同时也拓宽了可见光波段的研究领域.